Preparing to file your tax return

Who needs to file their tax return?

You normally need to send a UK Self-Assessment Tax Return if any of the following apply:

• You were self-employed or a partner in a partnership
• You received untaxed income, for example, property income, significant savings interest, dividends above the allowance, foreign income or chargeable capital gains
• You, or your partner, received child benefit and either of you had an adjusted net income over £60,000 in the year. The high-income child benefit charge (HICBC) applies on a taper and fully withdraws the child benefit by £80,000.
  

PAYE-only high earners: For 2024/25 and later, HMRC has removed the income threshold that previously forced PAYE-only employees to file because of high income. If your affairs are simple and all income is taxed at source, you may not need to file, but other triggers (such as dividends, property income or gains) still apply. Always check HMRC’s tool if unsure.

 

WHAT TO GATHER BEFORE YOU START FILING

Create a single folder (digital or paper) and collect the following:

• Employment: P60, P45 (if you’ve left a job), P11D/P9D or employer statement of benefits.
• Self-employment: income and expense records, invoices, bank statements, mileage log and details of any capital items. From 2024/25, the cash basis is the default for unincorporated businesses unless you choose accruals.
• Property: rental statements, mortgage interest, repairs, agent fees and dates for any property purchases/sales.
• Savings and investments: bank and building society interest, dividend vouchers or statements.
• Capital gains: contract notes, costs, improvement records, pooling calculations and details for any 60-day UK property capital gains tax (CGT) reports already filed.
• Pensions: personal contributions (grossed-up amounts), annual statements and evidence of relief at source. Higher-rate or additional-rate relief needs to be claimed through SA.
• Charitable giving: Gift Aid totals – higher-rate or additional-rate relief is claimed on your SA tax return.
• Student loans: plan type and any postgraduate loan.
• Child benefit: amounts received, and each partner’s income, where relevant to HICBC.
• Cryptoassets: dates, amounts, wallet/exchange records for disposals and income (staking/mining/airdrops). HMRC expects accurate reporting and is implementing new information reporting from 1 January 2026.

 

Keep paperwork for at least five years after the 31 January submission deadline for the relevant tax year.

 

STEP-BY-STEP: COMPLETING YOUR TAX RETURN ONLINE

1. Check access: ensure you can sign in to your Government Gateway and your unique taxpayer reference (UTR) is to hand.
2. Start early: you can file any time after 5 April. Early filing helps with budgeting and avoids last-minute errors.
3. Complete the main SA100 and add schedules you need (self-employment SA103, property SA105, capital gains SA108, etc.
4. Enter income and reliefs carefully.

• Savings interest: include gross interest. HMRC will apply the personal savings allowance (PSA) where due (£1,000 for basic-rate, £500 for higher-rate, £0 for additional-rate taxpayers).
• Dividends: the dividend allowance is £500. Above that, rates are 8.75%/33.75%/39.35%, depending on your band.
• Pension contributions: claim any higher/additional-rate relief not given at source.
• Gift Aid: enter the gross amount (what you paid plus 25%). The return adjusts your tax accordingly.

Rates, allowances and reliefs for the 2025/26 tax year

5. Review payments on account.
6. Submit and pay by the deadline. If you can’t pay in full, consider a Time to Pay arrangement online (this is usually available for Self-Assessment debts up to £30,000 if you meet conditions).

 

PENALTIES, INTEREST AND HOW TO AVOID THEM

• Late filing: £100 fixed penalty; after three months, £10 per day up to £900; at six and 12 months, further penalties (5% or £300, whichever is higher).
• Late payment: penalties of 5% of tax unpaid at 30 days, 6 months and 12 months, plus interest.
• Current interest: HMRC’s late payment interest is 8.00% from 27 August 2025.

If you cannot pay in full, set up a Time to Pay plan online to limit penalties (interest still accrues).

 

RATES, ALLOWANCES AND RELIEFS

Our next blog breaks down of the rates, allowances and reliefs for the 2025/26 tax year. Click to read.

 

FILING YOUR TAX RETURN

Filing early gives you time to check the numbers, correctly claim any reliefs or allowances, and plan for any payments on account.

Use the checklist, keep your records in one place and review any items that often get missed, such as savings interest, small dividends, Gift Aid and pension top-ups.

If you expect your income to fall, consider whether a payments-on-account reduction is sensible. If paying in full is difficult, look at Time to Pay before charges build up.

For support with the preparation of a Self-Assessment Tax Return, get in touch with your local TC Group office for a no-obligation quote.

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